1. Field of the Invention
This invention relates to the field of release agents for molded rubber articles and particularly to the use of silicone oils therefor.
2. Description of the Prior Art
Molded rubber articles generally are produced by compression molding, casting or extruding of vulcanizable intermediates. After the molded articles are vulcanized, it must be possible to easily remove them for the mold. For this purpose, silicone oils of average viscosity or emulsions containing such silicone oils are frequently used.
If the rubber material to be vulcanized is extruded in the customary manner, for example, in the manufacture of so-called long hoses which are extruded over plugs, such a release agent must have lubricating as well as release properties. The rubber material must not adhere to the plug nor may there be excessive friction as it slides over the plug.
Silicone oils or emulsions of silicone oils are not able to act as release agents and, at the same time, provide the necessary lubricating properties. In actual practice, dispersions of polytetrafluoroethylene (Teflon) in solvents have proven to be useful. The uniform and reproducible application of these dispersions on the surfaces which give shape to the articles does, however, create difficulties. In addition, the use of such dispersions is limited because of their high cost.